Initially known as cytokine synthesis inhibitor factor or CSIF, interleukin-10 (IL-10) is a potent immunomodulator of hematopoietic cells, particularly immune cells. Cells such as activated Th2 cells, B cells, keratinocytes, monocytes and macrophages produce IL-10. See, e.g., Moore et al., Annu. Rev. Immunol. 11:165 (1993). IL-10 inhibits activation and effector functions of a number of cells that include T cells, monocytes and macrophages. In particular, IL-10 inhibits cytokine synthesis, including that of IL-1, IFN-γ, and TNF, by cells such as Th1 cells, natural killer cells, monocytes, and macrophages. See, e.g., Fiorentino et al., J. Exp. Med., 170:2081-2095 (1989); Fiorentino et al., J. Immunol. 146:3444 (1991); Hsu et al., Int. Immunol. 4:563 (1992); Hsu et al., Int. Immunol. 4:563 (1992); D'Andrea et al., J. Exp. Med. 178:1041 (1993); de Waal Malefyt et al., J. Exp. Med. 174:915 (1991); Fiorentino et al., J. Immunol. 147:3815 (1991).
Multiple pathogens, particularly intracellular pathogens, elicit IL-10 production to slow or completely stall the effective removal of the pathogen by the immune response. Moore et al., Annu. Rev. Immunol. 11:165 (1993). For example, in blood lymphocytes from patients with HIV, leprosy, or tuberculosis, peripheral blood lymphocytes are typically anergic or nonresponsive in vitro when challenged with the pathogen. However, the neutralization of IL-10 in these demonstrated that an active effector response, i.e., Th1 reactivity, was present in these cells. Thus, it is believed that IL-10 is effectively commandeered by the pathogen to facilitate its infective state.
IL-10 is also associated with autoimmunity in vivo. Autoimmunity results from the development from autoantibodies, autoreactive T cells, or some combination thereof that target normal tissue. One example of autoimmune disease is systemic lupus erythematosus (SLE), a chronic rheumatic disease in which connective tissue throughout the body becomes inflamed. Autoantibodies that attack normal body tissue as if it were an outside invade result in the characteristic inflammation. While the precise cause is not fully understood, researchers believe it has both genetic and environmental components. Specifically, B-cell hyperactivity and the presence of various autoantibodies characterize SLE. Typically, IgG autoantibodies reactive to double stranded DNA (IgG anti-dsDNA abs) are elevated in patients with SLE. Between 60 and 70% of SLE patients produce IgG anti-dsDNA abs, some of which are nephrotoxic. SLE is ten times more prevalent in women than men, with symptoms ranging from facial rashes to disabling and potentially life-threatening organ dysfunction. It can develop at any age, but is most common in young adults.
Numerous studies support a role for IL-10 in the pathology associated with SLE. For example, while IL-10 is typically not produced by cells without appropriate stimulation, both B cells and macrophages from SLE patients spontaneously produce high levels of IL-10 in vitro. Llorente, et al., Arthritis Rheum. 40:249-60 (1997). In several studies, researchers demonstrated a correlation between serum levels of IL-10 and disease activity. Moreover, both in vivo and in vitro studies demonstrated that the blockade of IL-10 production can alleviate the clinical manifestations of SLE. See, e.g., Gonzalez-Amaro, et al. J. Autoimmunity 11:395-402 (1998).
Typically, immunoassays for high-concentration, high-molecular-weight analytes in the marketplace are predicated on the multivalence of the analyte. Ultimately, the analyte is detected by some sort of cross-linking, either by agglutination (in turbidimetric or nephelometric assays), precipitation (radial immunodiffusion), or sandwich immunoassays such as ELISAs.
U.S. Pub. No. US 2002/0142356 provides a method for obtaining anti-idiotypic monoclonal antibody populations directed to an antibody that is specific for a high-concentration, high-molecular-weight target antigen wherein said anti-idiotypic antibody populations have a wide range of binding affinities for the selected antibody specific to said target antigen and wherein a subset of said anti-idiotypic antibody populations can be selected having the required affinity for a particular application. U.S. Pub. No. US 20020142356 involves a competitive immunoassay of an antigen using an antibody as coat and an anti-idiotypic antibody as detection or vice-versa. Other references disclosing use of an anti-idiotypic antibody as a surrogate antigen include Losman, Cancer Research, 55 (23 suppl S):S5978-S5982 (1995); Becker, J. of Immunol. Methods, 192 (1-2):73-85 (1996); Baral, International J of Cancer, 92(1) 88-95 (2001); and Kohen, Food and Agriculture Immunology, 12(3):193-201 (2000).
There exists a need to detect humanized antibodies to cytokines such as IL-10 in biological samples without also detecting certain other antibodies directed or not directed to such proteins, particularly in clinical samples. The present invention fulfills this need by providing anti-idiotypic antibodies against humanized anti-IL-10 used in a detection assay to monitor levels of the humanized antibody in biological samples.